This invention relates to an image pickup system for use in combination with a craft, such as a spacecraft and an aircraft, flying over an object zone which is typically on the Earth's surface. Such an image pickup system is particularly useful in a remote sensing system for the Earth.
An image pickup system of the type described is used to remotely sense an object zone on board a craft flying over the object zone along a flying direction at a predetermined flight altitude. In a remote sensing system, it is often necessary to pick up a stereo image, such as a stereo topographic image, from the object zone by the use of the image pickup system. In order to provide the stereo image, the object zone should be picked up, along the flying direction at two locations spaced apart from each other, so as to form two optical images of the object zone.
A conventional image pickup system comprises a first signal producing system and a second signal producing system. The first signal producing system produces a first electric signal representative of a first partial zone of the object zone when the craft flies at a first time instant at a first location at which the first partial zone is viewed. The second signal producing system produces a second electric signal representative of a second partial zone viewed in the object zone when the craft flies at a second location at a second time instant which is later than the first time instant.
The object zone is typically on the Earth. The craft moves relative to the Earth. In addition, the Earth rotates while the craft moves from the first location to the second location. It is therefore possible to say that the object zone moves independently relative to the craft. As a result, the first and the second partial zones are different by a different zone. Consequently, the image pickup system is incapable of producing correct image signals for use in producing the stereo image of the object zone.